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POmodifying already initialised array of strings
 

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  1. POmodifying already initialised array of strings
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    <p>In the code below if i remove both strncpy its compiling and running without seg fault. But with strcpy its throwing seg fault. IN both cases i am trying to modify a read only address right ?Then why the unexpected behaviour ..</p> <pre><code>#include&lt;stdio.h&gt; #include&lt;string.h&gt; int main() { unsigned char* newPrompt="# "; static unsigned char* au1CLIPromptStrings [] = { "", "Login: ", "Password: ", "0123456789012345678901234", "0123456789012345678901234", }; /* here am trying to moodify the read only address */ au1CLIPromptStrings[3] = "# \0"; au1CLIPromptStrings[4] = "# \0"; /* removed two strncpy second time */ printf("a1 = %s and a2 = %s\n",au1CLIPromptStrings[3],au1CLIPromptStrings[4]); /* here using strcpy am trying to modify */ strncpy(au1CLIPromptStrings[3],newPrompt,strlen(au1CLIPromptStrings[3])) ; strncpy(au1CLIPromptStrings[4],newPrompt,strlen(au1CLIPromptStrings[4])) ; } </code></pre> <p>thanks in advance..</p> <p>There is one problem i am facing now. I need to pass the values of au1CLIPromptStrings to another double pointer which is bieng used in many places .So if i assign the address of au1CLIPromptStrings to that doublepointer of type unsigned char which is in a structure elemet.Now i am not able to retrive the elements its getting NULL evenif address is coming proper.I cannot use the same au1CLIPromptStrings varibale everywhere , Here is a proto of waht i told,</p> <pre><code> unsigned char **newPrompt1 =NULL; newPrompt1 = au1CLIPromptStrings; printf("a1 = %s and a2 = %s\n", newPrompt1[3],newPrompt1[4]); #include&lt;stdio.h&gt; #include&lt;string.h&gt; int main() { unsigned char *newPrompt="# "; unsigned char **newPrompt1 =NULL; unsigned char au1CLIPromptStrings [7][30] = { "", "Login: ", "Password: ", " 0123456789012345678901234", " 0123456789012345678901234", }; newPrompt1 = au1CLIPromptStrings; // here am assigning the address printf("b1 = %u and b2 = %u\n",newPrompt1,au1CLIPromptStrings); printf("a1 = %s and a2 = %s\n",newPrompt1[3],newPrompt1[4]); } </code></pre>
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    1. USkelvin
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    1. COI'm not sure what you're asking. Please show clearly the code that leads to behavior you don't expect, and why you don't expect it.
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    2. COFrom my point of view this should print the elements in `au1CLIPromptStrings`. So you mean it prints NULL for `newPrompt1[3]` and `newPrompt1[4]`?
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    3. COau1CLIPromptStrings values we can index and its proper also ,but for newPrompt1 values indexing is giving null values
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      1. USkelvin
 

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